The invention relates generally to tire loader apparatus, and more particularly to mechanisms for controlling the movement and positioning of loader shoes used with such apparatus.
Tire loaders are well known in connection with automated tire machinery such as tire presses. A tire loader is typically used to pick up a green or uncured tire and to position the green tire in a tire mold that is part of a tire press. A tire loader includes a loader basket having loader shoes that are used to hold each green tire, usually by exerting a slight pressure against the tire bead. This is accomplished by sliding or extending the shoes out horizontally to a position where they can engage the bead. After the green tire has been grabbed by the shoes, the loader is moved (typically in the vertical and horizontal directions) by an elevator frame to a position near the tire press mold such that the green tire is centered in the mold cavity. The shoes are-then retracted so that the green tire drops into the mold cavity. The loader is then moved back to its original position for retrieving another green tire while the tire in the press is cured. In a double tire process, two tire loader baskets are used to load two green tires in to the press during each transfer operation. An important feature of the tire loader basket design is the control mechanism used to move and position the loader shoes.
An example of a tire loader basket of the prior art is disclosed in U.S. Pat. No. 4,279,438 (the '438 patent) issued to Singh. In the '438 patent, the movement and positioning of the loader shoes is accomplished using a stationary horizontal support plate and a rotatable horizontal circular plate, with the latter being connected to the shoes by means of respective connecting rods or links. The shoes move radially by a sliding action on a corresponding number of horizontal slide bars when the circular plate is rotated. The circular plate is rotated in an oscillatory fashion by use of a piston cylinder having at one end a rod that is connected to the circular plate. The blind end of the cylinder is mounted on the support plate. The stroke of the cylinder rod thus determines how far the circular plate is rotated which in turn determines how far the shoes extend radially outward.
An important aspect of the control mechanism for moving and positioning the shoes is the ability to adjust the travel or radial extension of the shoes on the slide bars. This is needed because a typical loader basket is used to pick up tires of various diameters, so that the radial extension of the shoes must be adjusted for the particular diameter of the tire to be picked up. In the '438 patent the travel distance of the shoes is adjusted by means of a stroke limiting assembly. This assembly physically restricts the stroke of the piston cylinder to a preset amount by manual use of adjustable stroke limiting lock nuts.
Using the stroke limiting assembly described in the '438 patent, the extended position of the shoes can be set only by adjustment of the limit stops. This is because the loader shoe linkage mechanism is always connected to the piston cylinder via the rotatable circular plate. It would be difficult and impractical to move the shoes against the resistance of the cylinder. Therefore, the stroke limiting assembly must be separately calibrated so that the stops can be accurately positioned by the operator depending on the diameter of the tires to be picked up. The use of the mechanical stops also results in the piston cylinder not being used for its full stroke in most cases.
The objectives exist, therefore, for a tire loader shoe adjustment mechanism that can be more quickly and easily operated for accurate setting of the extended position of the loader shoes.